For example, JP-2003-254038A discloses this type of device. In an engine control system using a diesel engine with a diesel particulate filter (hereinafter referred to as “DPF”) as a PM removal filter, the device is adapted to estimate an unburned fuel amount or a DPF temperature for an engine based upon a required engine operating condition at the time of controlling an engine operating condition. More specially, this device is structured to have a map for defining a heat quantity corresponding to an unburned fuel amount and a DPF generating in a required engine operating condition sectioned by an engine rotational speed and an in-cylinder fuel injection quantity per one intake stroke for each required engine operating condition. In an actual engine operating, this device is adapted to determine the unburned fuel amount and the DPF temperature based upon an actual required engine operating condition by referring to this map.
However, in such engine control system, a required engine operation condition is not necessarily the same as an actual engine operating condition. For example, the engine control system includes some individual differences between cylinders in a multi-cylinder engine or individual differences in characteristic of control components between engines themselves. Further, in this engine control system, characteristic changes due to aging of control components. More specially in an injection quantity of an injector, there is generated a deviation (an injection quantity difference) between an injection quantity command value (required injection quantity) as a control target value and an actually injected fuel quantity due to individual differences or aging changes. In this case, the aforementioned device includes differences generated between a required engine operating condition and an actual engine operating condition, thereby resulting in generating more than a small estimation error in regard to the unburned fuel amount or the DPF temperature estimated based upon the required engine operating condition. Further, when an estimation error of the DPF temperature is great at the time of heating DPF (for example, at the time of burning PM trapped in the DPF as regeneration processing), the DPF may be damaged (melting damage) caused by excessive rise in temperature of the DPF.
In view of the above, there exists a need for an unburned fuel amount-estimating device for an engine and a temperature-estimating device of an exhaust emission purifier which overcome the above mentioned problems in the conventional art. The present invention addresses this need in the conventional art as well as other needs, which will become apparent to those skilled in the art from this disclosure.